For some time it has been known to provide a packaging film which contains antiblocking agents, such as particulate silica, in one or both outside layers of the film. These antiblocking agents offer two advantages. First, they help to prevent the film from sticking or blocking to itself when the film is rolled up on itself during the manufacture of the film. Second, the antiblock offers a beneficial "roller bearing" effect when the film is run across metal parts in typical commercial packaging equipment. An example of such equipment is a Doboy.TM. horizontal form/fill/seal machine.
Fatty acid amides, sometimes referred to as slip agents, are often also included in the film, in order to provide the film with a desirable film-to-film coefficient of friction, so that packaged products slide freely when in contact with one another. This is desired in order to facilitate alignment of packaged products for the bulk packaging thereof, for example in boxes, as well as providing a desired low film-to-equipment coefficient of friction.
Unfortunately, antiblock particulates on the surface of the film, as well as fatty acid amides, are believed to often slough off of the film and accumulate on the metal parts of food packaging machines. This undesirable build up on the metal surfaces sometimes results in scratching of the film. In extreme cases, tearing of the film occurs, rendering it unfit for its commercial purpose. The metal parts must be cleaned. This of course interrupts the continuous operation of the equipment, thereby increasing cost of production.
Abrasion of machine parts can also result from the use of films containing antiblocking agents in the surface layer, akin to the use of sandpaper on a metal surface.
In addition, the possibility exists for sluffing off of the antiblocking agent into the product being packaged in the film.
It is thus desirable to reduce or eliminate the presence of antiblocking agent on the surface of the film, while still providing the benefits offered by such agents.